Thread tension for sewing machines



June 13, 1944. s wo 2,350,995

THREAD TENSION FOR SEWING MACHINES Filed Oct. 5, 1942 Patented June 13, 1944 THREAD TENSION ron sEW Ne' Aoi 'mEs l M @Fred Ashworth} Wenham, Mass jassignor to United Shoe Machinery Corporation, Fleming ,ton', J., a corporation otNew Jersey I Application October 5, 1942, Serial No. 460,743

' Claims (01 112-59).

The present'invention relates to improvements in thread tensioning devices for use in sewing machines operating on shoes or other heavy Inaterials of the type employing a hook needle and a take-upacting to take up each loop of thread drawn through the work by the needle and to give up thread during each sewing cycle at a rate greater than required by the other stitch form-j ing devices, so that the portion of thread ene'ag'e' ing the take-up becomes slack during a part of each sewing cycle. An example-of a machine of this type is disclosed in U. S. Letter's Patentjlflof 2,271,611 of February-3, 1942, of which the present inventor is a joint patenteei "In'the machine of the patent, a thread tensioning device is'provided, acting on the thread between the'take-up and the point of operation; of'the needle in the work, to keep those portions;

of the thread engaging the stitch forming device's other than the take-up under control while the take-up is giving up threadto 'said other stitch forming devices-.- In order to avoid the efiects' of excessive friction and abrasion on the thread while the take-up is taking up thread and particularly'while a stitch is being set, mechanism driven from the main sewing shaft of the machine also is provided for actuating the tension to relieve'th frictional efiect of th tensioningdevice on the thread at certain times in each sewing cycle.

This invention has for an object to provide in a' shoe sewing machine,- means for controlling the tension on a sewing thread without the use of any actuating mechanism separate from the tensioning device; Other more general objects are to simplify and improve the construction of a lock-' stitchshoe sewing machine in such a way that it will operate not only more effectively and at higher speeds than heretofore, but will enable themachine to be threaded more easily and will a'void to a large extent incidentalresults of Wear on the operating machine parts;

While certain feature of the invention conin a sewing machine having a hook-needle, and

any :form of take-up with whicha variable tensioning device is provided, the action'of which device is-controlled-by transverse movement of the thread to change the degree of tension in the thread. A particularly efiective construction and arrangement is in a machine having a rotary take-up, the take-up stroke of which imparts a movement transverse to the thread length in one direction and the give-upstroke of which imparts-a transverse movement to the thread in the opposite direction. In its; preferred form, the tensioning device consistsbf a friction plate and a cooperating thread engaging block having surfaces arranged within the plane of rotation of'the take-11p and ofjsaid trahsversethread movement and yielding-means acting at one end of the plate nearest which the thread passes during the give-up stroke of the take-up to cause'maximum tension to be applied to, the thread during the give-up stroke When the thread'passes along the surfacestowards the other'end of the plate, the effect of the yielding means is continuously reduced'until a, position is reached where little or no tension is imparted to the threa'd. Thus, in

a sewing machine of the lockstitch type, little or no resistance is ofieredto movement of .thethread about a shuttle or loop takerafter theloop of needle thread engaging the loop taker'has been enlarged to its maximumsize and thetakeup has begun to take up the loop. In 'this'way, a particularly efiectiveconstruction of tensioning device is provided in which no actuating mechanism therefor driven by the sewing shaft is required and with the use of whichthe same of improved results are obtainable as compared to those in prior machines or the class disclosed in the patent above referred to. I 4

Other features of the invention reside in a novel andimproved tensioning devicev through which the thread may readily be introduced when the machine is being threaded, as a preliminary to placing the machine operation and. mother devices, "fcombinations and arrangements of parts hereinafter described and claimed, the advantages of which will be obvious from-the-I'ollowing description taken in connection with the accompanying drawing illustrating one embodiment of the invention.

Inthedrawin i r Fig.; 1 1s a sid .sectionaltview'looking from the left ofthe lower forwardportionof a lock'stitch shoe sewing-machine embodying the features of the present invention, parts havinggbeen removed and a side. cover platefor the rotary take-upihavingi'been swung :open tUeXposethetake-up duringits giVe-upstroke at avposition just-before the :asxa result of giving up needlethread at a rate 1 any actuatingn'i'echanis'm greater than required by the other stitch forming the take-up roll moves about the take-up shaft devices; l2 as a center in the direction of the arrow, the Fig. 2 is a similar view of the same parts indineedle thread, indicated at 22, will move first cating the take-up during its take-up stroke; and along the surface l8 towards the rear of the ma- Fig. 3 is a sectional plan view on an enlarged 5 chinebefore the take-up stroke of the take-up, scale of the tensioning device indicating the poas shown in Fig. 2, and towards the front of the sition of the needle thread during the give-up machine before the give-up stroke of the takestroke of the take-up. up, asshown in Fig. L To irnpart a frictional The machinefi'lliittrated in the drawing is a efidrtlori'thethifead, the threa d 22:15:. cornpressed lockstitch shoeoutsole sewing machine having a" 1 yildihgly by 'the'plate I6 secured to a stud 24 curved hook needle 2, a continuously rotating passing loosely through an opening in the block take-up 4, a looper 6, a thread finger 8, a shuttle M at right angles to the thread engaging surface ID containing a supply of; lgcking thread and; thereon fiurrounding the stud 24 is a coil spring other stitch forming'devices similar 'in constr cacting against the side of the block I4 and an tion and in mode of operatiom'efx'cfeiptfas; dr'em; aidjustingnutl8-threaded on the stud. after pointed out, to those dic'lbsiil'inft I "The'ar'r'angeinefit of the stud and plate is such above referred to. As in the machi'e ofthep t that during the give-up stroke of the take-up ent, the stitch forming devices are sp operated (Fig. 1*) the. thread; will be drawn nearer the that substantially no tension will be im arteg to stud than during the take-up stroke of the takethe needle thread in each sewing cyc e'eiice'pt uffYFigJZ). When the take-up has reached the WEE?, titittiibglt fi h iag m re h need e. nqsii l iiot i ,1 tr iye l g. h ea -im a eid bsea 'wl i ach 9. 1 s ein e xms an-Jl han e ili esl y t-ib the l tit w k had f as? ha a. at ite m aqbiae efie co eia ns nai bi' tl i. ea er ess as ea s. mended fi ilre hefill eedi n i a l q .9 e z nee -t w rt g atsef t. sletivs yeslee s ese s epft el: h S ensi aZl tf-g 9 1 112 P t 11)- thl ewigg l ve he ee just rec the 't readfciasel te n. e 2 a Qtz eflizfi c 11 291 b 't hejifigilq oorging qigeratienanse rey nts; QQCQIR isl d sd; need e e 2?. he, di ii a r tmi geasi3 o h ea th: the; neefl a e i h irem j r m teams; s agesneedle? br edgi neesi eum mh. 2 5; Wal t-segment hesl gl hread ivenlupt yi the take-up is drawn aboutth e thre adcase by,

fi ftw f f it-p essure, t gfl ghtgr p ree ne Wise!- ii it gifi a fiQMD JJPQKAE n e s; ureiaeingeffective'auriiiftiie ake-n11str l e or. 93e,? wr it i s ea e it mg hei mdtk thetakef-iim"Tfflmchafiisiii higt'fifj t ritqj 95m r m tiee.qf ii rea i he ee haileiri i't jfdie iii r i eia i a. :s o. res uxe he: ate: a ainsthe; i a f i ni min was iaa ama saievenwzmmteeai engineers; h ,Studt n aeinss lia l ckt form; a t lm wl b utwliiehJliepletep mnsssli htly sst Jetted mevesl great h ntbreet ieneaei i i xiaees-i With the threadii sl g itic i; o ii w'orknnuttt the drawing as a sho so1e I32 Thist" jon ng an device causestheffnedle tlii ftob'' relie ards ha iidz s bnsi esuastrqka fitk ei a aratfi 'onftheten j re sver almoxeme tt n hanopnositesdiiectmnj c i isei owa dsst e. nidsoiitheitakeeupsstroke to;

sioningd'evice'; Not onlyoo'es the :1 vi require 4 infrequent adjustment, but" when 1 rinslaee nl he thxeadeiatp,maximumdensimiinei necessary to replaceanyof 'theparts dueitowear; DQSi i IL en mil ethetmnsvniiseicmn einentmii'l a simple and easily accomplishedinterchange the thread on t hread en aging suriaceseoithi may be made without requiringdisconriectio of ns min evi eshe framej.'o; the, machine anyother'operatihgpaitsfifith m'ichih 'b fth'" orag Q1-l l 9 hfiri akfi-a gn nd iSsLCOIIeQ exercise or special-"precautions in reasseinbhng" structqdewith arguide surfaceflju andnthe block, replaced parts. 65 L arries a flanged guideQwheel, 32ivrotatabll The construction of the improved-needle thread n, houldered; QL WULMJ secund; withinfth tensioning device is: illustrated best in Fig, 3 and A block at L ight angles ..to. ,thesplan'e of. takegdp; comprises a block MAsecuredto-the framed the" rotations 'rne wneeitsziproiectsdhorizoii li b jil machine 'and la"fcooperating friction plate '|'6. ondt e llpnetl dgeioi thegterisionplate;I'GQ'thuSr. One side of theblockl M is formed withwai thread 7e pfl fleyentin escapeeotthe threaderearwardlygfroiui engaging surface l8. alongwhi'chnedlethr'ead betm enithe.plateandblock.a,

extendin betweentthe" looper. and .Lthe take-up Wherrintroducingjhreadintonthe machine in" movesl1;:Thethreadenga i gsurrace 18- lie'ss'iib reparati i orta .sewihgeoperationl theehlatiliga stantiallyrinia planemeflnedlbyihe circularlpath n qvedi learloi z-the guide, .wfieLaSZgandlthe 1 T 911 errhe annotthctakeaum sothatasw stuain is;made w tn -s mci nt ien tnrtabbtafit;

the requisite rmovementi -Tohold" the plate against rotation with the I stud. as a pivot, the forward endof theuplateis slotted to receivea pin'-36-carried by .the block |4 in parallel relationto the stud; ":i v 1. .1

.Due to; the pressure exerted on the thread when the thread; is: in its maximum frictional position nearest. .the stud 24, there is'a tendency to strip ilint from the thread and'for the .lintto collect around the stud. ,.'If this occurs, the.friction plate l 6 may be forced away from the block .114 so, that; improper tension, will be impartedito the thread To prevent; accumulation of .lint stripped from the thread from; affecting ,the thread tension adversely; the block M is recessed at'38 to form a channelthrougnwhich broken fiber endsof lint may. drop from b ,etween the p a eand bl I we By the construction ofatensioning device thus described the degree of friction imparted to the thread varies automatically between two, 1imit s as the transverse position of the thread changes along the thread engagingsurfaces of the block and plate- .No p wee dr v g ta n m p ar nismyfor-z ,thetensioning plates and no special adjustments to insure proper timing of the actuating mechanism are required as in the machine disclosed in the patent. The only adjustment to be made is in the tension of the spring 26 and once this is set by rotation of the thumb nut 28, no further changes are needed.

The nature and scope of the invention having been indicated and a particular embodiment thereof having been specifically described, what is claimed is:

1. In a sewing machine having a hook needle and a take-up acting to take up and give up thread and to move the thread transversely of its length, a tensioning device constructed and arranged to impart a variable tension to the thread, variation of which is controlled by transverse movement of the thread between the takeup and the work.

2. In a shoe sewing machine having a hook needle and a take-up, the take-up stroke of which imparts transverse movement to the thread in one direction and the give-up stroke of which imparts transverse movement to the thread in the opposite direction, a tensioning device constructed and arranged to impart a variable tension to the thread, variation of which is controlled by the transverse movement of the thread between the take-up and the work to increase the tension when the thread is moved transversely in one direction and to reduce the tension when the thread is moved transversely in the opposite direction.

3. In a sewing machine having a hook needle and a take-up acting to take up and give up thread and to move the thread transversely of its length, a tensioning device between the take-up and the work including a block and a plate having cooperating thread-engaging surfaces between and along which the thread moves, and yielding means near one end of the plate for exerting a varying pressure through the plate on the thread as it moves along said surfaces in a direction transversely of the length of the thread.

4. A shoe sewing machine having, in combination, a hook needle, a take-up comprising a rotary member arranged to move in a circular path, a thread engaging member on the rotary member acting to take up and give up thread to the needle and to impart transverse movement to the thread between the take-up and give-up strokes, anda tensioning idevice for the thread between "the thread engaging member and'the work includingia friction plate and a cooperating thread engaging block-having surfaces arranged withintheplane; of-rotation of the thread-enaging-member to :enable movement of the thread along said surfaces as the thread engaging member'is;,actuated, and yielding means acting at one. end 501 ,theplate nearest which the thread passes whilethe threadis being given up to cause a greater tension to be. applied to the thread while being given; up than while beingtaken up by the-take-up-.:-. a a .5. Ashoe sewing machine having, in combina tion; a hookneedle; a take-upcomprising alroe tarymember;;arrangedto move .in a'.circular path, a "thread engaging member. on the rotary memberaacting to take'rup and give up thread toith'e needle and tosimpart transverse movementzto-thethread between the take-upnand give-upstrokes, and'a tensioning. device forthe thread between the threadengaginglmember and the work "includingaixfriction plate andv a.. co- Operating. thread engaging block having surfaces arranged: within the plane of rotation of the thread engaging member to enable movement of the thread along the surfaces as the thread engaging member is actuated, a yieldingly actuated stud for securing the plate to the block at one end of the plate nearest which the thread passes while the thread is being given up to cause less friction to be applied to the thread while being taken up by the take-up than while being given up.

6. A shoe sewing machine having, in combination, a hook needle, a take-up comprising a rotary member arranged to move in a circular path, a thread engaging member on the rotary member acting to take up and give up thread to the needle and to impart transverse movement to the thread between the take-up and give-up strokes, and a tensioning device for the thread between the thread engaging member and the work including a friction plate and a cooperating thread engaging block having surfaces arranged within the plane of rotation of the thread engaging member to enable movement of the thread along the plate during actuation of the take-up, a stud loosely supported by the block secured to one end of the plate nearest which the thread passes while being given up by the take-up, and yielding means acting on the stud to impart greater friction to the thread when located nearer the stud than when passing between the plate and block at a greater distance from the stud.

'7. A shoe sewing machine having, in combination, a hook needle, a take-up comprising a rotary member arrranged to move in a circular path, a thread engaging member on the rotary member acting to take up and give up thread to the needle and to impart transverse movement to the thread between the take-up and give-up strokes, and a tensioning device for the thread between the thread engaging member and the work including a friction plate and cooperating thread engaging block having surfaces arranged within the plane of rotation of the thread engaging member to enable transverse movement of the thread along the plate during actuation of the take-up, yielding means acting at one end of the plate located at a position to impart greater friction to the thread while being given up than while being taken up by the takeup, and a thread uide 'forlim'itlng; transverse movement of the thread; while being taken up.

8; A shoe sewing maphinehaving, ineombihation, a. hook needle, a'take-up comprising afrotary'member arranged to move in aeircular'path} strokes, and a tensioning devicefor thethread between the thread engaging member and-the work including a friction plate and cooperating thread engaging block having surraeesarrsmg'ed within the plane of rotation "of" the thread engaging membertoenelble transverse, movement of .the thread along theplaite duringi'eletuati'on of the take-up; 9; Stud for "retainingthe plate on. the JDIOICR.) and means'f'for preventing'iint stripped from the thread i from ,"aeeuiiiuiating between .the? plate and bloekfabout thesti'u'd.v

Y 931121 aiiockstitoh shoe sevring 'iiiabhi'ne hav'ihg stitch forming: devices 'inclu'cliiag a "needleij a shuttlevend' a take-upacting'f' td"'ttike up and give-upfthread to" the shuttle; the "onibination with a i'tens'ioning" device Comprising a; "thread engaging" block'and aeooperating friction plate,

' a fthr'e'adl'guide onthevblock for limiting transverse movement of the Jthreadf along the plate, and aTspringmi-e'ssed.stud secured to the plate passing through the block and being '01 sumeientlen'g'th to enable the plate to be moved awayfromthe, block elear' 'of' the -guide while applying threadv to the" tensioning; device.

10'. In a loekstitch'shoe'sewing machine havingstitch"forining"devices including" a needle, a -'sli1 fitt1e 'and' a take-up actin to take-u and give up thread 'to' 'the' "shlittle,l the oinbination With' a rensionmg device" comprisin a thread engaging 'hlobkend aeooprating' friction plate, a threa ginaeon the blook for limiting transverse movement 'oithe' t'hi'ad' alohg'the plate, asprmg pressed stud seefired to the plate passing through the block and being "of sufficient lri'gth' to'enabie the'jilate to be m'cjiveaaway from the block"oieaijof'thefgiiide while applying thread to the 'tensiofiing devic and a pm mountedinparallerrelation to the stud onfthe hlook for engagingthe plate to prevent rotation of theplate' with the stud as a pivot. 

